HDR Photography Part 2 - Stitching Your RAW Images Together :: Digital Photo Secrets

HDR Photography Part 2 - Stitching Your RAW Images Together

by David Peterson 6 comments

In part 1 of this series - Capturing HDR Images, I showed you how to go out and get the five separate images that you will use for your HDR photo. Now I will show you how to put them together in Photoshop. In practice, this is a lot easier than you would think. That’s why I’m also going to show you how to convert a single RAW file into an HDR image so you can create HDR action shots.


There is some custom software available to merge your separate images into the one HDR photo. I like Photomatix and have heard a lot of good things about Dynamic Photo-HDR. Both software have free trial versions so you can give them a go.

Adobe Photoshop CS2 or later also has a HDR merge function. Once you open up all five of your RAW images, simply go to File --> Automate --> Merge To HDR. A box will pop up, allowing you to select a folder or the open files. Because we’ve already opened all five files, choose the “open files” option.

Merging the three images to the left creates the HDR image above. Thanks to Photomatix for the images.

Your only job after this is to step away and allow Photoshop to do its magic. In most cases, you will be working with images that are larger than 70 megabytes, so you can expect it to take a long time. When the merge is finished, you will be given a slider that you can move from the left to the right to pick which colors you want to emphasize the most. I usually just play with this until I find the most visually appealing version.

Once you like what you see, click O.K. You’re done. Now that was easy, wasn’t it? The file you now have is still in the RAW format, so you will need to save it as a JPEG if you want to share it with your friends. That’s all there is to creating HDR photos.

How To Create “Fake HDR” Shots

Here’s the real challenge. What do you do if you want to create an HDR effect with a single RAW image? Many photographers find themselves in this situation when they are shooting action. Because you can’t take five separate images at different exposure levels when your subject is moving, you need to figure out a way to cheat the system. Here’s how.

We are basically going to create a bunch of “fake” exposures by adjusting the brightness of our RAW image. First, go out and take your one RAW action shot. Open it up in Photoshop. Next, choose image --> adjustments --> brightness and contrast. You will only adjust the contrast to create the 5 or 9 different images you will merge later on.

The controls under brightness and contrast aren’t that sophisticated. This shouldn’t be a problem as long as you make all of your different exposures symmetrical. What do I mean by this? If you bump up the brightness by a factor of +10 for one of your fake exposures, you need to also include a fake exposure with a brightness of -10. Each incremental step up should have an equal and opposite incremental step down.

You are welcome to save as many of these files as you want. Most people stop at about 9. Once you have the 9 separate images, open them up in Photoshop and merge them to HDR as per the steps above.

There’s another way to do action shots without having to fake so much of it. If your subject only takes up a small portion of the frame, you can take all of the brighter and darker exposures without your subject in them. Then, once you get back to your computer, you can copy and paste your subject into the images with the different exposure levels.

This only works if you slightly brighten or darken your subject before pasting it into the photo. If your subject doesn’t match the light levels in the scene, the final HDR merge will look a little funny. This can take a lot of time. Most of the time, you may not be willing to spend hours and hours in front of a paint program to get these shots looking 'just right'. However, for those 'one in a million' shots, you might find the results worth it.

“Fake” HDR photos don’t look nearly as good as the real deal. That’s because you aren’t using any data. You’re just making it up. Photoshop doesn’t know what’s in the shadows. It just fills everything in. Whenever you can take the different photos for an HDR image, do so.

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Comments

  1. Sam says:

    A simpler way to 'fake' a HDR image is to use tonemapping in Photomatix. Open Photomatix, click File>Open select your single RAW file, click tonemapping.

    Photomatix will automatically create the under and over exposures you need from the RAW file. The process from here on in is the same as a genuine RAW image, the only difference is dependent on how good your camera is at recording information. When you bring up the shadows for instance, you may bring a lot of noise with it, on my D7 i get some pretty awful vertical banding. In a shot with a huge range of light this may be a problem. But for action shots, portraits, etc, there is little problem.

  2. andaja says:

    thanks , really needed

  3. David says:

    Good, very good. Thank you.

  4. Willie Nel says:

    Thanks David, a weekend of training & fun

  5. Vasantha says:

    Great ......

  6. Alastair M Seagroatt says:

    I use HDRtist - a free program on the Mac, very easy to use & seems to work well.

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